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Rok1215
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Double SSID on both 2,4 / 5 GHz band

Tue Mar 16, 2021 4:36 pm

Hello,

I've got a MikroTik wifi network of about 15 APs (9x wapAC, 1x CAP, 4x hap, 2x directional APs).
It was supposedly configured by another tech 5 years ago, with 2 SSIDs working on both bands at the same time.
On some APs only guest work on 2,4GHz, on some it only works on 5GHz, same goes for the main SSID, etc.
The issues have been there since this was setup, but now the owner wants it resolved.

Looking at the configuration and its a big mess, I see all 15APs have an additional interface set as slave and all the slave interfaces are setup for guest network.
What is puzzling me is that for both configs (for main and guest network) the band is not set. From looking at the status of the APs, they seem to be randomly choosing which band to currently use.

If the configurations do not have a defined band, do they use both?
If not, would I need to have basically 4 different interfaces on the same AP, to get both SSIDs working on both bands?
 
pe1chl
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Re: Double SSID on both 2,4 / 5 GHz band

Tue Mar 16, 2021 4:59 pm

In RouterOS, you will find that configuration for SSID etc is always done on some wireless interface, which always is only for one band.
Each band has its own wireless interface, and only when that band is supported on that particular device.
So you may find devices with a 2.4 GHZ device, with a 5 GHz device, or both.
And on each such device you can create a slave device to have a second SSID on that same band. It is not possible to have more than one SSID without such a slave device.
The slave device can be on the same network as the master, or it can be on another network, either by configuring a VLAN or by adding the slave device to a different bridge.
So indeed it is possible to make a very complex config, and when you do not know the original objectives or when the requirements have changed, it is easy to call it a mess.
You will need to identify what are the current requirements and how to configure that.
 
Rok1215
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Re: Double SSID on both 2,4 / 5 GHz band

Tue Mar 16, 2021 5:44 pm

In RouterOS, you will find that configuration for SSID etc is always done on some wireless interface, which always is only for one band.
Each band has its own wireless interface, and only when that band is supported on that particular device.
So you may find devices with a 2.4 GHZ device, with a 5 GHz device, or both.
And on each such device you can create a slave device to have a second SSID on that same band. It is not possible to have more than one SSID without such a slave device.
The slave device can be on the same network as the master, or it can be on another network, either by configuring a VLAN or by adding the slave device to a different bridge.
So indeed it is possible to make a very complex config, and when you do not know the original objectives or when the requirements have changed, it is easy to call it a mess.
You will need to identify what are the current requirements and how to configure that.
Hey thanks for the reply.

So with your comment I am certain the slave interfaces are the ones meant to be for the guest network.
(I call it a mess because some aren't even correctly set to be master/slave, some have a vlan tag set, some don't, etc..)

But I understand you correctly, this would mean for this to have been configured correctly from the start for both SSIDs to work on both bands, one AP should have 4 different interfaces on it?
Example:
AP1 Master interface - main SSID, 2,4GHz
AP1 Slave interface 1 - main SSID, 5GHz
AP1 Slave interface 2 - guest SSID, 2,4GHz
AP1 Slave interface 3 - guest SSID, 5Ghz
 
pe1chl
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Re: Double SSID on both 2,4 / 5 GHz band

Tue Mar 16, 2021 8:52 pm

No it would be like this:
AP1 Master interface 1 - main SSID, 2,4GHz
AP1 Master interface 2 - main SSID, 5GHz
AP1 Slave interface 1 - guest SSID, 2,4GHz
AP1 Slave interface 2 - guest SSID, 5Ghz

Usually the 2,5 GHz interface will be called wlan1 and the 5 GHz interface wlan2.
When you add slave interfaces they would by default be called wlan3 and wlan4 but you can rename those to e.g. wlan1-slave and wlan2-slave to it is clear to where they belong.
 
Rok1215
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Re: Double SSID on both 2,4 / 5 GHz band

Wed Mar 17, 2021 8:33 pm

So I went through the configuration today and it seems to be better now.
You were correct, on the APs by default wlan1 is the master interface for 2,4GHz and wlan2 for 5GHz.
Many of the interfaces were not labeled correctly in CAPSMAN and made troubleshooting a nightmare, had to sort them by their MAC addresses in the end.

One thing I still don't seem to understand is how the APs select which channel to use?
None of the interfaces have a channel set. Do these APs automatically scan and select which channel to use?
 
pe1chl
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Re: Double SSID on both 2,4 / 5 GHz band

Wed Mar 17, 2021 8:55 pm

When the frequency is set to "auto" it will do a quick scan on startup and select a channel that is least occupied.
It will not change that later when the situation changes, so it is of little use.
You can also select a fixed frequency and/or use a channel list to suggest frequencies is should use, e.g. channel 1, 6 or 11 on 2.4 GHz.

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